In vitro cellular immune functions are being studied in a masked method in patients with ocular toxoplasmosis, presumed ocular histoplasmosis, pars planitis, Behcet's disease, ocular sarcoid, birdshot choroidopathy, and chorioretinitis of unknown origin. Crude ocular antigens as well as the purified uveitogenic soluble antigen (S-antigen) of the retina are being used in a lymphocyte microculture technique in order to evaluate the presence of cellular immune memory to ocular tissues. Immune memory is also evaluated by the production of lymphokine in a capillary migration system. A subgroup of patients with posterior uveitis has been identified as having this immunologic memory. Other studies concentrate on the presence of suppressor cell activity functioning of macrophages and lymphocyte subsets as defined by monoclonal antibodies in these patients. These results shed light on the basic mechanisms of uveitis and may be used as a guide for specific immunologic therapy.